The invention concerns an axle having a bridge arranged underneath the wheel axle such as used in low-platform omnibuses. To obtain the deepest possible entrance in the omnibus, the bridge of the axle is situated deeper compared to the wheel axle. To be able to implement flexible driving drafts, it is advantageous to actuate each driven wheel via a driving engine located on the wheel. The width of said drive system determines the gear width in the omnibus which must not exceed a minimum width. It is, therefore needed to lodge a majority of the wheel drive, the same as the brake of the wheel, within the rim of the wheel.
German Patent No. 1,227,783 has disclosed an axle with a wheel drive where an electric motor is used as a driving engine which drives coaxially an inner central wheel of a first planetary step, the web of which drives an inner central wheel of a second planetary step, the web of which is connected with the wheel. A drum brake, situated coaxially around the electric motor, has been disclosed as a brake. The wheel forces are transmitted, via the housing of the electric motor, to a supporting part of the axle bridge in which the electric motor is inserted. The fact of the housing of the electric motor is inserted in the supporting part of the axle bridge and non-turnably connected therewith creates the possibility of wear of the connection fit between the housing of the electric motor and the supporting part, as a consequence of high force action due to the wheel force or contact corrosion of the fit. Besides, the use of a disk brake, instead of a drum brake, within the rim is not possible since there is no space for the actuation device of the disk brake within the rim. The disk brake, when used in said driving system, would considerably lengthen and result in a small gear width for the omnibus.
German Utility Model DE 295 18 401 U1 discloses an axle where a wheel is driven via an electric motor, the electric motor is located in the axle bridge. The axle bridge is situated underneath the wheel axle. But since the electric motor is located in the axle bridge, the axle bridge needs a sufficient total height in the area of the electric motor in order to accommodate the electric motor, and this has a disadvantageous effect upon the entrance height of the omnibus.
WO 98/40235 disclosed a driving system, specifically for omnibuses, in which each wheel of an axle is driven by at least one electric motor. The guide rods and spring carriers are connected with the axle bridge, and the axle bridge having a gantry distance. The driving engine is placed entirely outside the wheel rim whereby the driving system needs a considerable installation space.
The problem on which this invention is based is to provide an axle, especially for low-platform omnibuses, in which each wheel is driven by a driving engine, the wheel is decelerated via a disk brake and the axle configured so that the wheel drive can be mostly lodged in the rim, and the axle bridge needs only a small height in order to obtain the greatest possible gear width and a low entrance for the low-platform omnibus.
The problem is solved by an axle according to the preamble of the main claim and including the characteristic features thereof.
According to the invention the axle consists of a bridge arranged underneath the wheel axle and driving wheel respectively driven by a driving engine, preferably an electric motor or hydraulic motor. A disk brake, actuated by an actuation device, is located mostly within the wheel rim. The driving engine has an axle offset relative to the wheel axle whereby a space results, opposite to the axle offset, in which the brake and the actuation device thereof can be installed between the rim and the driving engine. The axle offset of the driving engine, relative to the wheel axle, is preferably designed downwards but can also be designed in, or opposite to, the driving direction whereby the position of the actuation device of the brake also moves. To provide the largest possible center distance, a reduction gear is preferably selected in which the driving wheel, which is driven by the driving engine, meshes via an intermediate wheel with one driving the ring gear. But the center distance can also be implemented via other reduction gears. The ring gear is preferably connected with the output via one other planetary step. By the fact that in the first reduction gear the gearwheel actuated by the driving engine meshes with the ring gear, a largest possible center distance is obtained and by the fact that the gearwheel actuated by the driving engine meshes in addition with one or two other intermediate wheels, the first reduction gear can be designed very compact since the torque produced by the driving engine is distributed among several tooth engagements. The housing of the driving engine is non-rotatably connected, on one side, with the hub carrier of the axle which absorbs the wheel forces and, on the other side, the housing of the driving engine has fastening means on which the axle bridge can be mounted, the same as suspension elements of the axle and guide rods. The suspension elements of the axle and the housing of the driving engine can also be designed as one piece. By the housing of the electric motor absorbing the wheel forces and relaying them via the suspension elements and guide rods, the same as the axle bridge, it is possible to select the axle offset of the driving engine relative to the wheel axle large enough to make it possible to install the disk brake, the same as a large part of the actuation device of the disk brake, within the wheel rim. Since the first reduction gear can be designed very compact, it is possible to place one part of the driving engine within the rim whereby a very compact driving system and a large gear width can be implemented for the omnibus. The housing of the electric motor transmits all the wheel forces. Thereby the axle bridge must not be connected directly with the wheel hub whereby the weight of the wheel drive is reduced and, due to the reduction of the masses without springs, an improvement of the driving behavior and a saving of the road cover occur. By the axle bridge not surrounding the housing of the driving engine and being directly connected with the wheel hub, it is possible to configure the housing of the drive engine so that the engine can be cooled by internal and external air ducts and the mounting of the energy supply for the driving engine be freely selected. The axle bridge is preferably designed as a rectangular section whereby a small height of the axle bridge results making a low entrance in the omnibus possible. Lower inclined guide rods are mounted on the axle bridge which can be flexibly fastened to the axle bridge by a welded plate. The plate can also be designed so as to be screwable on or cast on. By the wheel drive having two reduction gears available, which are preferably designed with helical cut teeth, it is possible to use a very compact driving engine of small construction length and diameter. By using helical-cut reduction gears, a silent driving is provided.